1. Technical Field
Embodiments relate to a driving circuit for selectively performing a pre-charge operation of a display panel, and a method of controlling an output of the driving circuit.
2. Discussion of Related Art
Display panels include liquid crystal displays (LCDs), plasma display panels (PDPs), organic light emitting diodes (OLEDs), or field emission displays (FEDs). Reducing power consumption is one of the major technologies for all display panels and a variety of methods are used therefor. A pre-charge technology is one of the power consumption reducing methods, in which, while a current output, for example, an N-th output, where N is a natural number, is maintained, the current output is pre-charged to a specific voltage before the current output is changed to the next output, for example, an (N+1)th output.
However, when the current (the Nth) output level and the next (the (N+1)th) output level are the same, if the current (the Nth) output level is changed to a pre-charge level and then to the next (the (N+1)th) output level, unnecessary power consumption is generated.
FIGS. 1A and 1B are waveform diagrams for explaining a conventional pre-charge operation. In FIG. 1A, an N-th output level A is output in response to an N-th input level, the Nth output level A is changed to a pre-charge level B in a pre-charge section, and an (N+1)th output level A is output in response to an (N+1)th input level. Although the N-th input level and the (N+1)th input level are not changed, pre-charge is unnecessarily performed. In FIG. 1B, the N-th output level A is output in response to the N-th input level, the N-th output level A is changed to the pre-charge level B in a pre-charge section, and an (N+1)th output level C is output in response to the (N+1)th input level.
FIG. 2 is a block diagram of a conventional driving circuit for explaining an example of a pre-charge operation method. In general, a display panel transmits and outputs an input signal for a frame. A driving unit 22 selectively outputs a first voltage V1 or a second voltage V2 as an output voltage OUT (an N-th frame output) in response to an input voltage level (an N-th frame input) input through an input unit 21.
The first control signal CTRL1 is a signal to control an output enable section in which a pre-charge operation is not performed. When a next input voltage level (an (N+1) th frame input) is input by the input unit 21, the driving unit 22 does not instantly change the output voltage OUT to a next output voltage level (an (N+1)th frame input). A pre-charge unit 23 is operated in response to the second control signal CTRL2. The pre-charge unit 23 changes the output voltage OUT to a third voltage V3 or a fourth voltage V4 that is a pre-charge level, in response to the second control signal CTRL2.
The driving unit 22 outputs the pre-charge voltage V3 or v4 according to the second control signal CTRL2 and does not output the first voltage V1 or the second voltage V2 in a specific section. When the pre-charge operation section designed corresponding to the specification of a product ends, the output voltage OUT pre-charged to the third voltage V3 or the fourth voltage V4 is changed to the first voltage V1 or the second voltage V2 of the driving unit 22 selected by the next input voltage level (the (N+1)th frame input) and is output as the (N+1)th frame output. The first voltage V1 or the second voltage V2 is output in response to the first control signal CTRL1 indicating the output enable section.
In the conventional pre-charge operation discussed above, unnecessary power consumption is generated when the current (the Nth) output level and the next (the (N+1)th) output level are the same, if the current (the Nth) output level is changed to a pre-charge level and then to the next (the (N+1)th) output level.